Six men have been arrested and face illegal gaming-related charges following the raid at a packed banquet hall in Markham, north of Toronto.

Police say the joint-forces investigation also shut down an offshore betting site called the Platinum Sports Book which they allege was being run by the group.

York Regional Police Supt. Paul Pedersen says almost $2.5 million in cash was seized after more than 400 officers executed search warrants across the Greater Toronto Area and as far away as London, Ont.

Pedersen says about 2,300 people had gathered at the hall, which had been turned into an illegal gaming house.

He says the people found in the hall were allowed to leave without charges, except for the six, whom police allege were profiting from the gaming operation.

He says 20 computers were seized at the banquet hall "where online offshore gaming was taking place, along with cellphones and business records."

Charged are William Miller, 49, Arno Thomsen, 45, and Shlomo Buchler, 40, all of Toronto; David Hair, 44, and Andrew Bielli, 48, both of London, Ont.; and Martin Spruce, 45, of Vaughan, Ont.

All six are charged with engaging in bookmaking, participating in a criminal organization, keeping a common gaming house and conspiracy to commit an indictable offence. They are scheduled to appear in court in Toronto on March 21.

"I want to be clear that this event last night was not open to the public. Online gaming in this fashion is not available to anyone," Pedersen said during a news conference Monday.

"Only those invited by the organizers of this criminal enterprise could attend and only those sponsored by this criminal organization could participate on the website," Pedersen said.

"Last night we were able to shut down that website. All traffic going to that website is now being redirected to (the police joint investigation) site."

"As of early this morning over 17,000 hits were registered at this website from illegal gamers trying to collect on their bets."

Acting RCMP Supt. Keith Finn said while there is legal gaming in Ontario that is properly managed and licensed, illegal gaming such as this alleged operation "lines the pockets of organized crime."